In constructing a fluid flow transfer device using a pleated membrane such as a hemodialyzer, it is desirable to anchor the membrane tips on the blood (or other fluid to be dialyzed) side to the apparatus housing interior to direct the blood flow into the membrane folds and prevent shunting of blood from inlet to outlet without being dialyzed in the folds. One problem has been development of a simple but effective method of anchoring the tips. One proposed solution has been to apply a thickened polyurethane potting over the surface of the housing interior through a hollow paddle-shaped spreader. However, this method is time-consuming, and potting is not uniform.